It is known to use refractory coatings to make refractory shells by coating expendable patterns (such as polystyrene or wax) and removing the pattern after curing the refractory shell. The refractorY shell is then cured chemically, by heating, or both. It is then used as a mold and/or core assembly to make a metal part by pouring molten metal into the mold and/or core assembly and allowing the metal to cool. The mold and/or core assembly is then removed.
In this process, the refractory coating is typically prepared from a refractory material, binder, and water at the site where the shell is to be made. The coating typically has a solids content of at least 50 percent by weight based upon the total weight of the coating. Coatings with higher solids contents (at least 55 percent by weight) are preferred because they minimize cracking. The problem is that increased solids level will generally result in higher viscosities which tend to make it more difficult to to adequately coat the shell. Although such refractory coatings produce effective shells and casings, they must be mixed at the site; they must be stirred regularly once prepared; and they are not storage stable once prepared.
A pre-mixed, storage-stable refractory coating would be useful because it would not require extensive mixing at the site and would not require regular stirring. Furthermore, if there were a power failure, the refractory coating would not agglomerate in the mixer forcing its time consuming removal.